Method for producing wellbore screen with tracer for fluid detection

ABSTRACT

A wellbore screen including: an apertured base pipe; an intermediate filtering layer including a plurality of metal fibers wrapped helically around the apertured base pipe and a fluid tracing filament wrapped helically about the apertured base pipe, the fluid tracing filament including a filament structure and a tracer carried by the filament structure, the tracer being entrainable produced fluids in a wellbore environment; and an outer apertured shell over the intermediate layer. A method for producing a wellbore screen, the method comprising: forming a filter tube by wrapping an intermediate layer, including a metal wool fiber strip and a fluid tracing filament, about an apertured base pipe in a helical arrangement under tension; positioning the filter tube within the long bore of an outer apertured sleeve; and securing the outer apertured sleeve and the filter tube together.

CROSS-REFERENCE

This patent application is a divisional of U.S. Non-Provisional patentapplication Ser. No. 13/711,307, filed Dec. 11, 2012, which is acontinuation of International Patent Application No. PCT/CA2011/000699,filed Jun. 13, 2011, which claims the benefit to U.S. ProvisionalApplication No. 61/353,983, filed Jun. 11, 2010, the entirety of allthree applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Wellbore screens may be used to filter out sand and like particulateimpurities from the produced fluid before the fluid is pumped to thesurface. If some form of filter is not provided for fluid entering thewell, sand and other impurities entrained in the fluid may materiallyreduce the effective life of the well pump and/or other apparatus towhich the well is connected.

SUMMARY OF INVENTION

In accordance with a broad aspect of the invention, there is provided awellbore screen including an apertured base pipe; an intermediatefiltering layer including a plurality of metal fibers wrapped helicallyaround the apertured base pipe and a fluid tracing filament wrappedhelically about the apertured base pipe, the fluid tracing filamentincluding a filament structure and a tracer carried by the filamentstructure, the tracer being entrainable in produced fluids in a wellboreenvironment; and an outer apertured shell over the intermediate layer.

In accordance with another broad aspect of the present invention, thereis provided a method for producing a wellbore screen, the methodincluding forming a filter tube by wrapping an intermediate layer,including a metal wool fiber strip and a fluid tracing filament, aboutan apertured base pipe in a helical arrangement under tension;positioning the filter tube within the long bore of an outer aperturedsleeve; and securing the outer apertured sleeve and the filter tubetogether.

It is to be understood that other aspects of the present invention willbecome readily apparent to those skilled in the art from the followingdetailed description, wherein various embodiments of the invention areshown and described by way of illustration. As will be realized, theinvention is capable for other and different embodiments and its severaldetails are capable of modification in various other respects, allwithout departing from the spirit and scope of the present invention.Accordingly the drawings and detailed description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

A further, detailed, description of the invention, briefly describedabove, will follow by reference to the following drawings of specificembodiments of the invention. These drawings depict only typicalembodiments of the invention and are therefore not to be consideredlimiting of its scope. In the drawings:

FIG. 1 is a simplified, partly diagrammatic plan view of an intermediatestage in one possible embodiment of the manufacturing method of thepresent invention;

FIG. 2 is a simplified elevation view of the apparatus of FIG. 1 with apart of that apparatus omitted to facilitate understanding;

FIG. 3 is a diagrammatic sectional elevation view taken approximatelyalong line 4-4 in FIG. 1; and

FIG. 4 is a sectional view of a wellbore screen constructed inaccordance with one embodiment of the invention.

DESCRIPTION OF VARIOUS EMBODIMENTS

The description that follows and the embodiments described therein, areprovided by way of illustration of an example, or examples, ofparticular embodiments of the principles of various aspects of thepresent invention. These examples are provided for the purposes ofexplanation, and not of limitation, of those principles and of theinvention in its various aspects. In the description, similar parts aremarked throughout the specification and the drawings with the samerespective reference numerals. The drawings are not necessarily to scaleand in some instances proportions may have been exaggerated in ordermore clearly to depict certain features.

FIGS. 1 and 2 are simplified, schematic illustrations of one possibleembodiment of an apparatus for manufacture of a wellbore screen suitablefor use in the production tubing of a subterranean fluid well, pursuantto the present invention. The apparatus of FIGS. 1 and 2 comprises anengine lathe 120 including a head stock 122 spaced from a tail-stock 124at opposite ends of a bed 126, FIG. 1. Lathe bed 126 may includesections 126A and 126B; see FIG. 2. The tail-stock 124 of lathe 120 maybe mounted on a carriage 128 in turn supported by wheels 130 engaging aguide rail 132.

The illustrated apparatus further includes one or more additional guiderails 133 and 134 that are parallel to but spaced from guide rail 132.There are also one or more carriages 135 and 136 that move along and areguided by rails 133 and 134, respectively. Carriage 136 supports asupply roll 138 of a strip 139 of metal filter wool; the metal woolstrip is described more fully hereinafter. The axis 140 of roll 138 isaligned, on carriage 136, so that strip 139 is at an acute angle Xrelative to the axis 142 of lathe 120 and the surface onto which it isto be applied. The carriage 135 on rail 133 supports a fluid pressurecylinder 144 having a piston rod 145 that carries a pressure plate 146that is further described hereinafter. Two stop members 148 may beprovided to assure accurate positioning of tail stock carriage alongrail 132.

In other embodiments, rollers may be employed to ride along the screenand apply compressive force to the screen fibers as they are laid down.A guide may be employed to guide the fibers to the screen.

The first step, in the method of the invention, is to provide apreselected length of an apertured base pipe 150, which serves as thecentral support for the wellbore screen. Base pipe is selectedeventually to be connectable into a longer pipe that is subsequently toserve as the production tubing for a subterranean well. Base pipe 150 isapertured along a section 152 thereof to permit fluid flow through theside wall of the pipe between its outer surface and its inner bore.Apertures may be in various forms and arrangements includingperforations, channels, slots, underlay, nozzles, etc. For example, theapertures may allow for open, unrestricted fluid flow or controlledflow, for example as by use of ICD technology. In FIGS. 1 and 2, theapertured portion has a length L. Length L usually exceeds one foot(25.4 cm) but may be shorter. Generally, length L is always much greaterthan the outer diameter of the base pipe. At the outset, pipe 150 ismounted in lathe 120 with the apertured section 152 of the pipepositioned between head stock 122 and tail stock 124, as shown in FIGS.1 and 2.

It is usually desirable to mount a single-layer tubular metal meshfoundation member 154, not shown in FIGS. 1 and 2 but shown in FIG. 3,about at least the apertured portion 152 of the pipe between the headstock and tail stock of lathe 120. The metal mesh foundation 154 may bemounted on section 152 of the pipe before or after the pipe is mountedin lathe 120.

The next step in the inventive method is to wrap a plurality of metalfibers around section 152. In the illustrated embodiment, the pluralityof metal fibers are arranged in a form that can be handled as a strip139 and possibly withstand a pull tension. For example, in oneembodiment the metal fibers may be in the form of metal wool, forexample in one embodiment, a compressed, felt-like filter wool. The woolmay be made of ordinary steel fibers, stainless steel fibers, or othermetal (e.g. brass) fibers. The best operational life is usually achievedwith stainless steel metal wool. With a metal wool filter material apassage size can be selected so that sand and like impurities cannotpass through the filter, but fluid flow is not cut off. The wool stripmay have dimensions to suit a given application. Typically, the metalwool strip is formed from fibers having an average thickness of 85microns and an average length of about one meter or less. The filterwool strip is often four inches (10 cm) wide and about 0.125 inch (0.3cm) thick, but those dimensions are subject to substantial variation. Acommon diameter for a storage roll of the wool fiber strip is about 1.5feet (0.5 meter) when the roll is full.

In one embodiment, the next step is to align the wool strip 139 at anacute angle X to the pipe axis, which is also lathe axis 142, at the endof the pipe onto which the wool is to be applied. The end of the metalfilter wool strip is then affixed to one end of the aperture portion ofpipe 150, by welding or other means. In FIG. 1, this has been done bymounting the wool strip storage roll 138 on carriage 136 with its axis140 at the desired angle to position strip 139 to extend away from thepipe at the acute angle X. Lathe 120 is now actuated to rotate pipe 150as indicated by arrow D, FIGS. 1 to 3. Rotation of pipe 150 pulls thefilter wool strip 139 from its storage roll 138 in the direction ofarrow E. Strip 139 is maintained under tension while being wrappedhelically around apertured section 152. FIG. 1 shows an intermediatepoint in the method of wrapping of a first layer of the metal wool striponto the pipe. Throughout the wrapping operation cylinder 144 and piston145 urge plate 146 toward the pipe in the direction of arrow H (FIGS. 2and 4) to aid the maintenance of tension in strip 139 and assure firmpacking of layers of the strip around the pipe.

A first layer of the filter wool strip 139 is wound onto the aperturedsection 152 of pipe 150 throughout its length L. Throughout thisoperation, strip 139 should be maintained under tension. Plate 146 andits operating mechanism 144, 145 may be sufficient for this purpose;however, some drag on the rotation of the wool supply roll 138 or othermeans for assuring maintenance of tension on strip 139 may be necessary.Throughout the winding of all layers of the metal wool strip onto thepipe 150, the carriages 135, 136 should be moved along paths parallel tothe pipe (see arrows F and G) so that a uniform helical winding isaffected. That is the purpose of guide rails 133 and 134 and theirengagement with carriages 135 and 136, respectively.

When a complete first layer of the metal wool strip 139 has been woundtightly onto the full length L of the apertured pipe section 152, thedirection of movement of carriages 135 and 136, which has been from leftto right as seen in FIG. 1, is reversed. Thereafter, a second layer offilter wool is tightly, helically wound onto the apertured pipe. Whenthe second layer is complete, the direction of movement of the carriages135 and 136 is again reversed and a third layer is started. Thealternate, back-and-forth carriage movements are repeated, with pipe 150rotating continuously in lathe 120, until the desired number of helicallayers of metal wool are superimposed upon each other around theperforate section 152 of pipe 150. The number of layers used is a matterof meeting the filter requirements for a given application; preferably,there should be at least five layers and often as many as ten layers,fifteen layers, or even more. Because the lathe continues to rotate inthe same direction throughout the process, while the carriage 136 movesthe strip back and forth, each alternate wrapped layer will be helicallywound in a direction opposite to the one applied directly therebelow,such that the layers overlap in a criss-crossing manner.

A fluid tracing filament 151 is also wrapped about the perforatedsection 152. A fluid tracing filament, also called a bio-tracer, is asubstrate that carries a unique tracer that is picked up from thesubstrate by fluid passing thereby, carried to surface with the fluidand can be detected at surface to provide information concerning thewell such as type of fluids produced, location of production, etc.

Fluid tracing materials may include a tracer embedded in a carrier suchas a polymer resin. The carrier is a solid and is readily handleablesuch that it can be placed in a screen in a position to retain thetracer carried therein also in that position. The resin is selected tosubstantially withstand downhole conditions. The resin can be watersoluble, water insoluble, formable in various ways, etc. It may be anadvantage to make use of water based resins for the water solubletracers. One reason for this is that the tracers are more easilydistributed into a hydrophilic resin than a hydrophobic resin.

The tracers can offer various operational attributes. They can haveselected solubility, a selected mode of detection, a selected responseto incorporation in a carrier substrate, etc. Separate tracers exist forhydrocarbons and water, including for high temperature liquids (i.e.steam) vs. lower temperature tracers, for gas/condensate vs oil, etc. Atracer can, therefore, be selected to only be picked up by water and/orhydrocarbon. As such, if it is desired to monitor for water flowseparately apart from oil flow, a particular tracer can be employed toonly be picked up and carried in water flow but not in oil. Of course,the selection of oil monitoring over water, steam over liquid water,etc. is also possible, as desired.

The tracers can be detectable in various ways. Tracers can beradioactive, non-radioactive, chemically detectable as by use oflaboratory or onsite analysis such as by chromatography, for example asby use of gas chromatography, etc.

Tracers can be incorporated into the polymer structure in any of variousways. The tracers, for example, tracers may be mechanically distributedas salt crystals in the polymer matrix, may be chemically incorporatedor a combination of both cases may be possible.

The tracers may be picked up by solubilization, erosion, chemicalreaction, etc. For example, chemically bound tracers may be releasedthrough hydrolyses either as the tracer itself or as derivatives of thetracer when the polymer is exposed to water at high temperature.

The rate of tracer pick up depends on a number of factors including,filament surface area and geometry of that surface exposed to the fluid,fluid temperature, fluid composition, fluid pressure and the mode oftracer infiltration to the carrier.

Generally, tracers that are chemically bound will be released at aslower rate than a tracer that is present as salt particles only.Chemically binding a tracer into the carrier, therefore, extends thelifetime of the tracer source. In cases where a long release period isdesirable, a chemically bound tracer/matrix may be preferable to otheroptions.

In one example, fluid tracing materials useful to form a fluid tracingfilament are available from Resman AS (Trondheim, NO). As an example, afluid tracing material may include a tracer carried in a polymer formedof melamine formaldehyde (MFR) condensate. The tracer may be mixed intothe MFR solution before hardening with a suitable hardener. Thecondensate solution is commercially available from suppliers such asDynea ASA, Norway, and is a reaction mixture of melamine, formaldehyde,methanol and water. It may also contain additives such as stabilizers,fillers, plasticizers and/or colorants. In one embodiment, the originalcontent before condensation is 25-40% melamine, 25-35% formaldehyde and1-10% methanol. The hardener can be formic acid or other products fromthe supplier. One possible product is Prefere 4720™ with addition of 10%(w/w) of the hardener Prefere 5020™ from Dynea ASA. The condensatesolution can also be prepared by mixing dried powder of the condensatewith water. The dried powder is available from Dynea ASA or othersuppliers and is made by spray drying of a condensate solution with thesame original composition of ingredients as listed above. One possibleresin powder product is Dynomel M-765™ from Dynea ASA. The tracer may bemixed into the condensate solution using a mechanical blender before thehardener is mixed in. In one embodiment, after embedding the tracer inthe carrier material, the material is cured under heat, for example, ina curing oven. The tracer release rate from this MET/tracer system willdepend on the surface and geometry of the MFR exposed to the fluid. Therelease rate of tracer will further be influenced by parameters such astemperature, fluid composition and pressure. The MFR will tolerate alarge fraction (in %) of tracer compound and still maintain acceptablemechanical properties. Typical tracer loading will be 5-20 weight % A. Astandard temperature/pressure range where the MFR system according tothe present invention may be used will be up to 120° C. and 600 bar.

Some tracers such as amino naphthalene sulfonic acids and fluoresceinwill react with formaldehyde and melamine in the condensate solution.The chemical reaction may be enhanced by applying heat. These tracerswill be incorporated into the polymer structure after hardening.

Of course, other tracers and substrates may be employed, the foregoingbeing only an example.

For example, urea formaldehyde resin was also tested as carrier for thewater tracers. This resin type was determined to be much less stable towater at elevated temperatures than MFR.

A more hydrophobic resin like polymethylmethacrylate was also tested asa carrier, but it was more difficult to disperse the tracer particlesevenly in the resin.

The fluid tracing filament can be wrapped about the base pipe at anystage in the process before, with or after wrapping of the wool.

If desired, the filament may be applied only with a portion of the totalwool applied to the base pipe. The filament may be applied to the basepipe above or below (as shown) the strip of wool 139.

In one embodiment, the filament is wrapped with wool strip 139, as it iswound onto the apertured section 152 of pipe 150 throughout at least aportion of its length L. Throughout this operation, the filament shouldbe maintained under tension. Generally, the tension is generally equalwith that of the strip. In one embodiment, the filament is wrapped withthe wool strip over at least two lengths of the apertured section. Assuch, the tracer carrying filament is present over substantially thefull length of the filtering area of the screen and in at least twohelical winds, one in a first direction of travel and one in a seconddirection of travel. Because the filament is being wound with the strip,as the strip is applied to the base pipe, the filament will be appliedin at least two helical directions such that in the final screen, thefilament is at least in part surrounded by (embedded in) the filterfibers and applied with regular spacing between each adjacent wrap suchthat they become criss-crossed as the second helical wind is appliedover the first. Because the filament is wrapped with the filter strip,the filament wraps are spaced apart with filter fibers between. Thewrapping process ensures that the filament is substantially consistentlydistributed throughout the possible fluid path through the filteringmedium, both along the length and through at least a portion of theradial thickness of the filtering area, such that at least some parts ofthe filament are certainly to be directly in the fluid path, even if thefluid is not passing evenly through the screen and even if the fluid istaking a substantially direct radial path through the screen, withoutmuch residence time.

In one embodiment, the fiber strip and the filament may be combined in asingle feed reel. In another embodiment, the filament is held in asupply, such as reel 153, separate from the reel of the wool strip, butis carried on carriage 136 and allows the filament to be in positionadjacent the strip just before the step of wrapping on the base pipe sothat they are applied together. For example, the filament may be fedinto the wrapping process and carried along with the pulling tension ofthe wool until a sufficient amount of the filament is applied. In oneembodiment, for example, the filament is introduced with the wool stripat an acute angle X to the pipe axis generally starting at an end of thelength of the apertured section 152. The leading end of the filament canbe affixed to the pipe or filter fibers or can simply be tucked into thewraps of the screen. In FIG. 1, this has been done by mounting the reel153 on carriage 136 with its axis at the desired angle to positionfilament 151 to extend away from the pipe at the acute angle X. Lathe120 is actuated to rotate pipe 150 as indicated by arrow D, FIGS. 1 to3, and this pulls the filter wool strip 1139 and the filament 151 fromtheir storage rolls simultaneously in the direction of arrow E. Strip139 and filament 151 are maintained wider tension while being wrappedhelically around apertured section 152. FIG. 1 shows an intermediatepoint in the method of wrapping of a first layer of the metal wool striponto the pipe with the filament underlying the strip. Tension may bemaintained by plate 146 and its operating mechanism 144, 145 may besufficient for this purpose and/or some drag may be placed on therotation of the wool supply roll 138 and reel 153. Throughout thewinding of all layers of the filament and the string onto the pipe 150,the carriage 136 should be moved along a path parallel to the pipe (seearrow G) so that a uniform helical winding is affected.

When a complete first layer of the metal wool strip 139 and filament 151has been wound tightly onto the full length L of the apertured pipesection 152, the direction of movement of carriage 136, which has beenfrom left to right as seen in FIG. 1, is reversed. Thereafter, a secondlayer of filter wool and filament is tightly, helically wound onto theapertured pipe. When the second layer is complete, the direction ofmovement of the carriages 135 and 136 is again reversed and a thirdlayer is started. The alternate, back-and-forth carriage movements arerepeated, with pipe 150 rotating continuously in lathe 120, until thedesired number of helical layers of metal wool and filament aresuperimposed upon each other around the perforate section 152 of pipe150. The filament wrapping may be discontinued while the metal stripcontinues to be laid down.

Filament 151 is of a thickness and strength to permit wrapping about thebase pipe. In particular, filament 151 has an elongation to breakselected to permit the filament to withstand the tension wrappingconditions to be used in the manufacturing process. At the same time,the filament may be selected to be incorporated into the screen withoutadversely affecting its filtering characteristics. In one embodiment,the filament is in the form of a coupon, narrow strip or line such ashaving a thickness to width ratio of 1:3 to 1:1. Alternately, the tracermaterial may be embedded in the wool strip.

In one embodiment, filament 151 is a line having a cross section withsubstantially a 1:1 thickness to width ratio (i.e. circular, square,triangular, etc. cross section) of 1 to 5 mm, for example, about 2 to 3mm in diameter.

In one embodiment, two filament types are used in each screen: a watertracing filament and an oil tracing filament. The amount of tracingfilament installed in the screen may depend on the duration to bemonitored and the volumetric flow of the oil or water to be monitored. A5 to 50% filament fill of the available volume is sought, amountsgreater than that tending to have less than acceptable sand screening.In one embodiment, a 15 to 20% filament fill was found to beparticularly useful, while the remaining volume was filled withfiltering material. For example, in one screen with a 5.5″ base pipediameter and a 10 ft filtering area length, about 100 m of a watertracing filament and 100 m of a oil tracing filament were used to fill17% of the available volume, with the remainder volume being occupied byfilter fibres. Each filament type was applied in a discreet length andin one embodiment, a plurality of filaments were applied in spacedside-by-side relation. In one embodiment, four filaments, two of oiltracing character and two of water tracing character are fed onto thescreen, at the same time.

FIG. 4 is a longitudinal sectional view of a wellbore screen 240constructed in accordance with the invention. It includes a section ofapertured base pipe 252 having a length L formed as part of or connectedto a pipe 250 of the production string.

In this embodiment, there is a tubular mesh 254 around the exterior ofthe base pipe 252, throughout the length L in which there areperforations 255 extending through the wall. Outwardly from the mesh 254is an intermediate layer including a plurality of layers 256 of metalwool fibers disposed in overlapping relation to each other. Layers 256are each formed from a strip of metal wool fibers wound helically, undertension, around the apertured pipe 252 in a manner such as thatdescribed above. While three layers are shown in FIG. 4; fewer or morelayers of filter wool may be used, depending on the application in whichfilter 240 is used. The wool layers filter out sand and other impuritiesfrom fluid passing into the interior of the filter's base pipe and outthrough pipe 250.

Along with layers 256, a fluid tracing filament 251 is also wrappedabout pipe 252. In this embodiment, two filaments 251 are incorporatedin a length of the first layer wrapped onto pipe 252, but they can beinstalled in other or further layers, as desired.

A tubular shell 260, having a length L and a plurality of apertures 262,such as perforations, channels, underlays, or slots, fits tightly overthe outermost layer of the intermediate layer, in this case theoutermost layer is of filter wool 256. A cap 264 may be provided at theend of pipe section 252 opposite the outlet afforded by pipe 250.

In operation of filter 240 of FIG. 4, the screen is secured in aproduction string. Other similar screens and/or screens without tracingfilaments may be installed along the string. Fluid with sand or otherentrained impurities enters apertures 262 in shell 260 as indicated byarrows M. The fluid passes through the multiple layers 256 of filterwool, leaving the entrained sand and other impurities behind. Thefiltered fluid enters the central, open area in pipe 252 through itsapertures 255 and flows out of the filter, as indicated by arrows N. Ofcourse, a pressure differential across the plural layers of filter 240is necessary for sustained, continuous flow, but that is necessary forvirtually any filter. Moreover, the flow is reversible, with the samefilter effect.

The mesh 254 between pipe 252 and the plural layers 256 of filter woolserves a definite purpose in filter 240. If there is no mesh 254, thefluid may tend, over time, to develop relatively larger passages betweenat least some of the outer apertures 262, in shell 260, and the innerapertures 255, in pipe 252. That passage enlargement may reduce theeffectiveness of filter 240, with the result that less sand and otherimpurities are filtered out of the fluid traversing the filter.

At the same time, tracers from the fluid tracing filaments 251 may, ifthey are soluble relative to the fluid, be picked up by the passingfluids and carried to surface in flow N. The screen, therefore, alsoprovides a monitoring system, wherein a unique tracer can be used thatallows individual zones in a well where the screen has been installed tobe monitored for amount and/or type of production flow. For example, aplurality of screens can be installed, each with a unique tracer in thefluid tracing filament installed therein. The screens with uniquetracers can be installed at known locations in the well and the fluidsproduced therethrough can be monitored as to flow rate and content byobservation of the tracer content in the fluid at surface. The tracersare designed to be released to the target fluid during a certain periodthat can be hours, days, months or years depending on the monitoringobjectives.

Unique tracers may be placed in each zone, or even in each completionstring joint to obtain the required downhole resolution. For example, ina well with three zones, at least three different tracers T1, T2, T3,may be used in screens intended for installation one tracer type foreach zone. If production arises from all zones, all three tracers T1,T2, T3 are present in the fluid arriving at surface. However, if onlyone or two of the tracers are detected in the produced fluids atsurface, this indicates that one zone is not producing and the locationof the non-producing zone is apparent, depending on which tracer is notpresent in the produced fluids.

The filaments may be selected to release their tracers to the targetfluid, oil or water, following certain events or over a certain periodof time depending on the monitoring objectives.

Samples of the well fluids are taken at surface for analysis.Commingling of several zones or wells does not jeopardize the results.Analysis is done and results are available quickly.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to those embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein, but is to beaccorded the full scope consistent with the claims, wherein reference toan element in the singular, such as by use of the article “a” or “an” isnot intended to mean “one and only one” unless specifically so stated,but rather “one or more”. All structural and functional equivalents tothe elements of the various embodiments described throughout thedisclosure that are known or later come to be known to those of ordinaryskill in the art are intended to be encompassed by the elements of theclaims. Moreover, nothing disclosed herein is intended to be dedicatedto the public regardless of whether such disclosure is explicitlyrecited in the claims. No claim element is to be construed under theprovisions of 35 USC 112, sixth paragraph, unless the element isexpressly recited using the phrase “means for” or “step for”.

We claim:
 1. A method for producing a wellbore screen, the methodcomprising: forming an intermediate layer of a filter tube, includingboth wrapping a metal wool fiber strip and wrapping a fluid tracingfilament, about an apertured base pipe in a helical arrangement undertension; positioning the filter tube within a long bore of an outerapertured sleeve; and securing the outer apertured sleeve and the filtertube together.
 2. The method of claim 1 wherein the metal wool fiberstrip and the fluid tracing filament are wrapped simultaneously aboutthe apertured base pipe.
 3. The method of claim 1 wherein the aperturedbase pipe has an aperture section and the metal wool fiber strip and thefluid tracing filament are wrapped simultaneously about the aperturedbase pipe over at least two lengths of the apertured section.
 4. Themethod of claim 3 wherein the fluid tracing filament is applied over atleast two lengths in a first helical winding in a first helicaldirection and a second helical winding in a second helical directionsuch that the first helical winding and the second helical windingbecomes criss-crossed along the length.
 5. The method of claim 1 whereinat least some amount of the fluid tracing filament is surrounded by themetal wool fiber strip.
 6. The method of claim 1 wherein the fluidtracing filament is in the form of a line having a thickness to widthratio of 1:3 to 1:1.
 7. The method of claim 1 wherein the line hassubstantially a 1:1 thickness to width ratio and of 1 to 5 mm indiameter.
 8. The method of claim 1 wherein the fluid tracing filament isa water tracing filament.
 9. The method of claim 1 wherein the fluidtracing filament is an hydrocarbon tracing filament.
 10. The method ofclaim 1 further comprising incorporating a second fluid tracing filamentin the intermediate layer.
 11. The method of claim 10 wherein the fluidtracing filament is either an hydrocarbon tracing filament or a watertracing filament and the second fluid tracing filament is the other ofan hydrocarbon tracing filament or a water tracing filament.
 12. Themethod of claim 10 wherein incorporating the second fluid tracingfilament in the intermediate layer includes wrapping the second fluidtracing filament about the apertured base pipe in a helical arrangementunder tension simultaneously with the fluid tracing filament.
 13. Themethod of claim 1 wherein the fluid tracing filament is 5 to 50% ofmetal wool fiber strip volume in the intermediate layer.
 14. The methodof claim 1 wherein wrapping includes securing a starting end of themetal wool fiber strip to the apertured base pipe; rotating theapertured base pipe about its axis to apply a pulling tension to themetal wool fiber strip to draw the metal wool fiber strip in a helicalorientation onto the apertured base pipe; and incorporating the fluidtracing filament with the metal wool fiber strip to also be pulled ontothe apertured base pipe as it rotates.
 15. The method of claim 1 whereinthe metal wool fiber strip and the fluid tracing filament are eachcarried on a supply reel that rides along an axis parallel to theapertured base pipe.